Growth and longevity of Lithophaga lithophaga: what can we learn from shell structure and stable isotope composition?

Abstract

Longevity of bivalves has been an intriguing issue, especially for those species of interest for human consumption. Reliable age and growth estimates often require the combination of several methods. In this study, we analyzed changes in shell structure including ridges on the external shell surface and growth lines observed in acetate peel replicas of shell sections of the European date mussel Lithophaga lithophaga, as well as the oxygen and carbon isotope values (δ18O and δ13C) of the shell. High variations in growth rates between individuals were noted. Ontogenetic ages of analyzed shells varied from 10 to 54 years (30.6–93.6 mm). According to results of generalized von Bertalanffy growth function, L∞ was 107.6 mm, and k was 0.03 year−1. δ18O results strongly suggest that growth ridges visible on the external shell surface of L. lithophaga are formed annually. The δ18O values ranged from −0.2 to 2.7 ‰ (\(\bar{x} = 1.15 \pm 0.72\) ‰), which equates to a temperature range of 13 °C. The reconstructed seawater temperatures (Tδ18Oshell) ranged between 12 and 25 °C, a range in good agreement with measured temperature. Stable carbon isotope values decreased through ontogeny and ranged between −2.05 and 2.32 ‰ (\(\bar{x} = 0.01 \pm 0.89\) ‰). Results of this study provide the first stable isotope data for L. lithophaga shells and show the potential of this species as a geochemical sclerochronological archive.

Notes

Acknowledgments

This research was funded through Croatian-French Program “Cogito,” project “Lithophaga lithophaga (Bivalvia; Mytilidae), archive of environmental changes in the Mediterranean.” Dr Elizabeth Harper performed mineralogical analysis of the shell. Authors are grateful to Ivica Matijaca, Igor Isajlović, Toni Mašće and Clémence Royer for logistic help with sample collection. We thank Michael Maus for help with processing the samples and Dr Paul Butler for help with language editing.

Compliance with Ethical Standards

Sampling permits were obtained from all relevant Institutions in Croatia. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted. All authors approved the final version of the manuscript and consent to submit has been received from all co-authors and institutions.